Elastocon offers rubber and plastic testing services

We have been accredited for 13 rubber testing methods, see our Testing Overview. It is SWEDAC, the Swedish Board for Accreditation and Conformity Assessment, that performs the accreditation. SWEDAC’s website says the following about what it means:

“To be accredited, skills, procedures and methods are tested so that all quality requirements are met as a standard. Next, Swedac check regularly that the company continues to meet the requirements for their accreditation.

The purpose of accreditation is to ensure that certification, inspection and testing is done with high quality and safety for life, health and environment. Accreditation means that inspections are performed impartial, accurate and based on internationally recognized standards.”

The photo above shows Ann-Cathrine Magnå, Elastocon's Laboratory Manager, who has 20 years of experience in polymer testing from SP Technical Research Institute of Sweden (RISE since beginning of 2017) in Elastocon’s testing laboratory.

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Estimation of lifetime from relaxation tests

Stress relaxation tests are ideal for making lifetime estimations using an Arrhenius plot. How to do an estimation of lifetime of rubber materials using an Arrhenius plot is described in the standard ISO 11346.

When doing an Arrhenius plot, tests are made of a critical property at different times and at least at three test temperatures. The tests are normally run until the properties are reduced to 50 % of the original value, see figure.

Stress Relaxation test at three temperatures of a per-fluoro rubber.

Arrhenius plot – a graph with logarithmic time on the Y-axis and 1/T on the X-axis, where T is the temperature in Kelvin.

Click images to enlarge.

The time to reach this level is determined for each temperature.

The test temperatures are chosen so the test time for the highest temperature is at least one week and the time for the lowest temperature is about 3–9 months.

The times to reach the ”end of life” time for each temperature are plotted in an Arrhenius plot, which is a graph with logarithmic time on the Y-axis and 1/T on the X-axis, where T is the temperature in Kelvin, see figure.

A straight line is drawn through the points and extrapolated to the temperature of use, to obtain an estimation of the life-time of the tested material.

Hardness testing

The rubber’s hardness or stiffness (modulus) is determined by measuring how far a blunt measuring probe can be pressed into the rubber.

Originally there were several methods for hardness measuring, today however there are mainly two methods used, and a third for measuring hardness on big rubber covered rolls.

Shore ISO 7619

IRHD ISO 48

Pusey & Jones ISO 7267

Tensile, compression and tear testing

Tensile testing according to ISO 37 is normally used to determine the following properties of rubber materials:

Stress at a particular elongation, e.g. 100 % or 300 %, expressed in MPa, is sometimes called the “rubber modulus”.

Tensile strength in MPa, which is the strength at break.

Elongation at break in %.

Compression testing according to ISO 7743 measures the rubber’s stiffness, spring constant or modulus. It can be done in modern tensile testers, which can be used in both tension and compression. The normal method is to deform the rubber by 25 % and measure the force.

Tear testing according to ISO 34 determines the tear resistance of the material. Three methods are common, namely: